Incorrect Voltages - Where to start

[azmouse76]

So I am picking backup a project that I started a year ago and never finished.

Everything is assembled. Apparently something is not perfect.

Resistance test looks good, however when I get to the voltage test on p77, things are off:

Point (Expected) = Actual

Left
kreg (1VDC) = 0.58
breg (100VDC) = 0
OB (100VDC) = 216
bA (0VDC) = 0
OA (170VDC) = 0
IA (225VDC) = 307

Right
kreg (1VDC) = 0.013
breg (100VDC) = 0
OB (100VDC) = 216
bA (0VDC) = 0
OA (170VDC) = 0
IA (225VDC) =307

Any ideas where to start?

Thanks

-dan

 

[Paul Birkeland]

Are all the tubes glowing?

 

[azmouse76]

Thanks for jumping in.

No Glow.

The Shunt Regulator Board LED's A-D2 and B-D2 seem about 50% dimmer than the led's on the Plate load boards and the A-D1 and B-D1 are about 75% dimmer than the plate load boards. 

 

[Paul Birkeland]

If the tubes don't glow, then you can forget about debugging any of the PC boards except the power supply board at the back.  Do you get 6.3V DC on the two pads labeled as such on the power supply board?  (There was a check for this in the manual early in the manual)

 

[azmouse76]

Thanks, noticed a mistake, swapped the 6922 and 12BH7.

Put in the proper sockets, the 12BH7 glows, however the 6922 does not. Looking at the data sheets, it seems the 6922 could now be bad given the voltages it saw in the 12BH7 socket.

Seem reasonable?

I ordered a new 6922 and will see what happens!

 

[Paul Birkeland]

The 6922 can be somewhat difficult to see glowing.  When you had it in the 12BH7 socket, you weren't supplying any heater voltage at all to it, so it may be worth revisiting with the lights in the room off, just to be sure.  I would also check your voltages now. 

 

[azmouse76]

No visable glow with lights on on the 6922.

Voltages are now:

Left
kreg (1VDC) = 0.027
breg (100VDC) = 0
OB (100VDC) = 213
bA (0VDC) = 0
OA (170VDC) = 219
IA (225VDC) = 221

Right
kreg (1VDC) = 0.0
breg (100VDC) = 0
OB (100VDC) = 212
bA (0VDC) = 0
OA (170VDC) = 220
IA (225VDC) =222

 

[Doc B]

Try turning the lights out and check again.

 

[azmouse76]

haha...sorry, lights were off....evidently in more way then one!